1. Technical Field
This invention relates to an engine control system.
2. Background Art
For better engine operation and for reducing undesirable exhaust gases, it is necessary to control the air fuel ratio. To control this air fuel ratio, a determination of air going into the engine is desirable.
Various airflow meters for measuring air intake into an internal combustion engine are known. For example, known types include a vane meter, a hot wire airflow meter and a vortex shedding airflow meter. Also known is a speed density calculation technique. In such a calculation, a measurement of pressure in the intake manifold is made, the air density is determined and the engine speed is determined to calculate the amount of air being inducted into the engine.
These known systems of airflow measurement have various drawbacks such as inaccuracy at extreme ranges of airflow either very high or very low, particularly due to dynamic range requirements. Introduction of exhaust gas recirculation (EGR) gases can also cause inaccuracies in some airflow calculations, as can changes in volumetric efficiency and air leaks in the induction air system. These are some of the problems this invention overcomes.